Hi Frances, those gnats are having a grand old time because your soil is staying damp. They don't really cause any trouble in and of themselves from what I understand, but your begonias may dislike having their feet so damp. You may wish to try moving them into a better draining medium or adding an inch or so of sand to the top of your pots. Sorry, I don't know anything about B. U205. Elizabeth?

Nigella thanks, I'll certainly let the soil dry, for now I'm going to spray the soil with something. The little devils make me itch, yuk!

Hiya, guys--I'd heard the same thing, Nigella, about them being virtually harmless, EXCEPT for their larvae. Seems the larvae likes to feed on healthy little roots....bad larvae!

I loathe the things, and have to fend them off of my african violets (lots of damp soil there!) all the time. I started adding about a tablespoon of household systemic insecticide to my soil mix supply (about 1 tblsp. per 10 cups mix) and that did the trick. I still see them on rare occasion, but the swarms are gone, gone, gone! And, the amount of insecticide is unnoticeable at all--a concern for me, with 3 little kids, a cat and 2 dogs. =)

Kathleen in TX

Apparently U205 is a rhizomatous species from Panama. I've never seen it before. If yours is a trailing/scandent then it probably isn't U205. Where did you find it? I would consider it rare, since I haven't seen it in 25 years of growing begonias.

Here is a link that might be useful: {{gwi:440350}}

I purchased U205 at our branch sell here in Sacramento in Oct. I'll post a picture later if I can understand the instructions.
Frances

I have controlled gnats with sand. Cover the soil with a quarter inch of sand and they will no longer reproduce. I have also keep their population under control with fly tape. It works great, however unsightly it may be...

Thanks all. I have some fly tape that I will hang. We had some nice sunny days last week that allowed me to put the affected plants outside. I purchased at least 40 plants at the convention sale in Aug and 15 more at our branch sale in Sep...I've kept busy washing pots,repotting and taking plants inside.

Elizabeth this is my U205.
Frances

Here is a link that might be useful: U205

Frances,
Your picture looks more like B. 'Boomer', which is a rhizomatous (B. soli-mutata) crossed with a thick-stem (B. reniformis). The leaves on your plant are pustular, like soli-mutata, while those of B. 205 are not.

At some point, two different people made the same cross that produced B. 'Boomer'. I don't know if the cross was made the same way (i.e. same pollen parent and seed parent). In any case, the resultant plants that circulated had different characteristics, proving that even if you cross two species you can get some variation. So one person's 'Boomer' may not look exactly like another's and may not have exactly the same growth habit.

I could be wrong about your plant, but it does look like 'Boomer' to me. It has the same sprawling growth habit and pustular leaves as soli-mutata and the thick stems of reniformis.

Elizabeth

Elizabeth, I think you're right about b. Boomer. Do you think I can propagate a leaf since it has a rhiz parent?

It's worth a try. Ordinarily I would say, "Of course you can.", but someone told me she had no success when she tried it. That doesn't mean it's impossible, though. You can also propagate stem cuttings.